Mortgage Calculator
Model mortgage payments with grace periods, staged rates, and equal-payment or equal-principal repayment.
Model a home loan in detail: set the amount and term, an optional interest-only grace period, one or more interest-rate stages, and choose equal total payment (annuity) or equal principal repayment. See the monthly payment, total interest, and a full amortization schedule by year or month.
Estimates only. Principal and interest, excluding taxes, insurance and fees.
Enter the loan amount and total term in years, then set an optional grace period (months of interest-only payments) and one or more rate stages — each with its own duration in months and annual rate. Switch between equal payment and equal principal to compare how the monthly amount and total interest change, then scroll the amortization table to check any specific month or year.
Formula & methodology
Equal-payment: M = P · i / (1 − (1 + i)^−N), with P the balance, i the monthly rate, and N the remaining months; recomputed whenever the rate changes.
The schedule is simulated month by month. During the grace period only interest is charged; equal-payment loans re-amortize the outstanding balance whenever the rate changes. Property tax, insurance, and PMI are not included.
Worked example
- $300,000 at 6.5% for 30 years → ≈ $1,896.20 / month — Total interest ≈ $382,633 over 360 payments.
Assumptions
- Each rate stage applies for the exact number of months you enter; whatever term is left uses the final stage's rate.
- The grace period is interest-only — no principal is repaid, and interest still accrues in full.
- Property tax, homeowners insurance, PMI, and HOA dues are excluded from the payment shown.
- The schedule assumes no extra payments, refinancing, or missed payments over the full term.
Common mistakes
- Treating the note rate you enter as the APR — APR also folds in fees and points, so it's usually higher.
- Assuming the grace period is free; interest keeps accruing and is due monthly even though principal isn't.
- Expecting equal principal to start lower than equal payment — it actually starts higher and decreases over time.
Frequently asked questions
What are the grace period and staged rates?
A grace period is an initial interest-only phase. Staged rates let you set a lower introductory rate for the first months and a different rate afterwards, matching many real mortgage offers.
Equal payment vs equal principal?
Equal total payment keeps every instalment the same. Equal principal repays a fixed amount of principal each month, so early payments are higher and then decrease.
Does this include property tax and insurance?
No. It covers principal and interest only. Escrow items vary by location and should be added separately.
How is APR different from the note rate used here?
The note rate is what this calculator applies to your balance each month. APR is a broader measure that adds in lender fees, discount points, and some closing costs, spreading them over the loan term — useful for comparing offers, but not the number to plug in for your monthly payment.
What happens to payments once the grace period ends?
The loan switches from interest-only to full amortization. With equal payment, the instalment rises so the shorter remaining term still pays off the balance. With equal principal, the fixed principal portion stays the same but the interest portion — and therefore the total payment — starts falling every month.
Privacy
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Disclaimer: Estimates for educational purposes only, not financial or lending advice.